When electric devices and metal interconnections included in organic or inorganic phosphors, displays, and photovoltaic devices, etc. are in contact with external chemical substances such as oxygen or water, they are modified or oxidized, and thus cannot be properly functioning. Accordingly, it is necessary to protect the electric devices from the chemical materials. To this end, a technique of protecting internal electric devices vulnerable to the chemical substances using a glass plate as a substrate or a cover plate has been proposed. The glass plate has satisfactory characteristics including light transmittance, coefficient of thermal expansion, and chemical resistance. However, since glass is heavy, hard, and easily breakable, it should be carefully handled.
Accordingly, there are active attempts to replace the glass plate used as a substrate for an electric device with a plastic film or sheet, which is a representative material having a lighter weight, superior impact resistance, and higher flexibility, compared with the glass plate. However, it is necessary to complement deficient physical properties of a plastic film commercially produced these days, compared with the glass plate. Particularly, it is most urgently necessary to improve water resistance and gas barrier properties among the physical properties of the plastic film, compared with the characteristics of the glass plate, and a barrier film showing excellence both in gas barrier properties and light transmittance is required.